1. Field of the Invention
The present invention relates to a coordinate input apparatus and a coordinate input-output apparatus in which an input screen is indicated by an input indicator such as a pen and a mouse so as to detect a positional coordinate indicated by the input indicator to be output to a personal computer and the like.
2. Description of the Related Art
Various types of conventional coordinate input apparatus are known, which are classified by a detection principle based on a physical phenomenon for detecting a position of the input indicator. As are also classified in the International Patents Classification (IPC), such main types are tablets as a resistance tablet, a magnetic coupling tablet, a capacitive coupling tablet, an optical coupling tablet, and an acoustic vibration tablet. The detail description of each type is omitted because the resistance tablet is disclosed in Japanese Patent Laid-Open No. 5-53715; the magnetic coupling tablet in Japanese Patent Laid-Open No. 5-289806; the capacitive coupling tablet in Japanese Patent Laid-Open No. 5-80921; the optical coupling tablet in Japanese Patent Laid-Open No. 5-53717; and the acoustic vibration tablet in Japanese Patent Laid-Open No. 5-66877, for example.
Each type of conventional coordinate input apparatus mentioned above is provided with means for generating each kind of physical phenomenon arranged in the input screen itself or between the input indicator and a part of the input screen. That is, the input screen of the resistance tablet has a stacked structure of two or more glass plates or plastic films opposing each other and having transparent resistors; in the magnetic coupling tablet, a sensor surface positioned in the input screen or below the input screen (the bottom surface of display means laid up on the input screen, for example) has loop-coil-shaped transparent electrode patterns in the X and Y directions; the input screen of the capacitive coupling tablet has line-shaped transparent electrode patterns in the X and Y directions; in the optical coupling tablet, optical units, each having a light source and a light-receiving unit, are arranged on both sides of the upper part of the input screen so that a direct vicinity of the input screen is scanned with light; and in the acoustic vibration tablet, an acoustic wave or an elastic wave emitted from or entered to the input indicator is transmitted through the direct vicinity of the input screen or within the input screen.
Due to the means for generating each kind of physical phenomenon arranged in the input screen itself or between the input indicator and a part of the input screen, as described above, there has been a problem that the conventional coordinate input apparatus described above becomes extremely expensive when increasing the area (i.e., size) of the input screen.
That is, the resistance tablet is required to form a transparent resistor having a uniform resistivity over the entire input screen; the magnetic coupling tablet and the capacitive coupling tablet are required to have loop-coil-shaped or line-shaped transparent electrode patterns in the X and Y directions uniformly arranged at equal intervals; in the optical coupling tablet, in order to scan the direct vicinity of the input screen with light in parallel with the input surface, the optical unit fine adjustment with high accuracies and the precise positional adjustment or positioning of the lateral optical units are needed. In the acoustic vibration tablet, when an acoustic wave is transmitted in the air, the air temperature control and the precise positional adjustment or positioning of plural detection sensors are required; when an elastic wave is transmitted within the input screen, in order to maintain the transmission speed constant regardless of the transmission distance, the material of the input screen requires high uniformity.
In the coordinate input apparatuses described above, there is a so-called input-output coordinate apparatus in which the input screen is integrally laid with a display screen such as a CRT, a liquid display, or a plasma display of a personal computer, enabling the personal computer to be input by directly drawing or pointing a figure on the display screen. When the conventional coordinate input apparatus is formed as an input-output integrated type, problems are as follows.
That is, in the resistance tablet, the brightness and clearness of display images are reduced because of the insufficient light-transmission rate of the resistor such as an ITO forming the transparent resistor; in the magnetic coupling tablet and the capacitive coupling tablet, the loop-coil-shaped or line-shaped transparent electrode patterns arranged in the X and Y directions are liable to be electrically and magnetically affected by noises from a panel, a driving circuit, or a power supply circuit of the display apparatus, resulting in unstable detection or further increased cost due to the unstableness prevention.
In the optical coupling tablet and the acoustic vibration tablet, a space is necessary for arranging the optical units or the detection sensors in the input screen, so that the entire apparatus shape needs to be harmonized.
Also, in the optical coupling tablet and the acoustic vibration tablet, there is an operational problem that when a hand of an operator or another article is placed into the transmission path of light, an acoustic wave, or an elastic wave, the detection performance is deteriorated or the detection cannot be established due to this effect.
As means for improving or avoiding the problems mentioned above proposed is a coordinate input apparatus comprising a coordinate plate having coded coordinate information recorded thereon and an input indicator having detecting means for detecting the coordinate information built therein.
For example, Japanese Patent Laid-Open No. 61-262832 assigned to the same assignee of this application discloses that square regions, each having at least nine divisions arranged in a matrix arrangement so as to draw a different pattern corresponding to a coordinate point on a coordinate plate, are further arranged in a matrix arrangement and are read by a coordinate indicator having a light-emission element and a light-receiving sensor built therein so that the direction and distance of the relative movement are detected depending on the changes in the pattern.
Also, Japanese Patent Laid-Open No. 61-296421 assigned to the same assignee of this application discloses that a different information corresponding to a coordinate point is positioned in each division distinguished on a coordinate plate in a matrix arrangement and is detected by a coordinate indicator so as to identify an absolute coordinate position. Japanese Patent Laid-Open No. 61-296422 assigned to the same assignee of this application also discloses that at least two kinds of information are positioned on a coordinate plate so that the amount of information is continuously changed in the direction different from each other and is detected by a coordinate indicator so as to identify an absolute coordinate position. Japanese Patent Publication No. 5-80010 discloses that from an optical stylus comprising a light source and picking up means, a passive-locator tablet having a tablet-address-cell (TAC) comprising an X-Y coordinates pair coded into a digital form and being dispersed on plural surfaces so as to be recorded forever, means for defining a TAC boundary by a spiral search, and means for periodically sampling TAC data, a pair of perfect TAC data (an X-Y coordinates pair) from TAC data sampled by Bresenham's search are produced, so that data producing means having a video memory for memorizing video images and a code-dot-image having a memory and stylus optical system subdivision stored therein produce the width of plural pixels in both directions. The Publication also discloses that the passive-locator tablet can be assembled in the front of the display surface, and that the tablet is formed from a plastic and the TAC is formed in the display side, i.e., the backside of the tablet while a glass layer is pasted in the front.
However, in the conventional coordinate input apparatus described above and comprising the coordinate plate having coded coordinate information stored therein and the input indicator having means for detecting the coordinate information built therein, two problems arise as follows. The first problem is about the reliability of the recorded coordinate information concerning the basic function of the coordinate input apparatus.
That is, in the recorded coordinate information, it is necessary that essential conditions concerning the detection by the detecting means such as the shape and clearness be semi-permanently maintained. When the recorded coordinate information is damaged, deformed, worn out, paled, discolored, and dropped off, it is extremely difficult to maintain the precise detection. Furthermore, the basic function of the coordinate input apparatus is damaged causing miss-detection or non-detectability. For example, it is obvious that the input indicating means be abutted, pressed, or rubbed against the surface of the coordinate plate or the tablet by an operator during the operation, so that when the surface of the coordinate plate or the tablet is provided with the coordinate information recorded thereon, the apparatus becomes extremely expensive in order to endure the actions described above for a long period.
When the back surface of the coordinate plate or the tablet is provided with the coordinate information recorded thereon, extremely careful handling is necessary to avoid damaging, paling, discoloring, and dropping off the coordinate information in the effective input region which dominates most of a plate member during the various manufacturing processes such as assembling, storing, and transportation after recording the coordinate information. This results in an extremely expensive apparatus. Moreover, when the back surface of the coordinate plate or the tablet is provided with the coordinate information recorded thereon, in order to use the tablet as a single unit on a desk, etc., it is necessary to endure the contact, abutment, and friction with various articles on the desk, resulting in an extremely expensive apparatus.
The second problem is that when the apparatus is formed as an input-output integrated type by laying the coordinate plate or the tablet with the display apparatus, as described above, due to the coordinate information recorded on the coordinate plate or the tablet, the brightness (luminance) of display images is reduced, the clearness (resolution) of display images is reduced, the reflection of extraneous light is increased, and the operability of input indication is reduced by being disturbed by the coordinate information when an operator can recognize it.
As for the problems described above, in Japanese Patent Laid-Open No. 61-262832, Japanese Patent Laid-Open No. 61-296421, and Japanese Patent Laid-Open No. 61-296422, the reliability of the coordinate information described above is not suggested, so that the first problem cannot be avoided by these disclosures.
Also, in these three disclosures, although the coordinate information positioned in the coordinate plate is suggested, the input-output integrated type with the display apparatus and the effect of the coordinate information on the display images are not suggested, so that the second problem cannot be avoided by these disclosures.
In Japanese Patent Publication No. 5-80010, although it is disclosed that as a structure having the excellent resistance to wear, the tablet is formed from a plastic and the TAC is formed in the backside of the tablet while a glass layer is pasted in the front, the problem in the manufacturing processes as the first problem and the problem in using the tablet as a single unit are not suggested so that the first problem cannot be sufficiently avoided by the disclosure.
Also, in Japanese Patent Publication No. 5-80010, it is suggested that in the input-output integrated type with the display apparatus, it is preferable that a gray grade caused by the TAC be uniform over the entire tablet, and binary codes for that reason; however, none of the method and means for reducing the gray grade which largely affects the display images is suggested. That is, there is a problem that the gray grade caused by the TAC affects the clearness of display images. As for this problem, according to the embodiment of Japanese Patent Publication No. 5-80010, if the tablet is 1 m×1 m in size; one dot of a corner cube indicating “1” is φ24 μm; the TAC is 7×7 dots, i.e., 250×250 μm in size, when in order to unify the gray grade in one TAC, 25 corner cubes are formed, the area ratio of the corner cubes in the entire tablet area is approximately 20%, resulting in the largely inverse effect on the clearness of the display images. As is suggested in the embodiment, the degree of freedom of the TAC format is maintained within the range of recognizing X and Y coordinates; however, it is for the degree of freedom of high-density code-data format which is one of the objects of Japanese Patent Publication No. 5-80010, so that the second problem is not suggested.